Hello,
I try to build Python 3.3 on OpenBSD, and it failed to build these modules: _socket (so _ssl too).

Errors are:
/home/remi/dev/cpython_test/Modules/socketmodule.c: In function 'sock_recvmsg':
/home/remi/dev/cpython_test/Modules/socketmodule.c:2935: error: storage size of 'iov' isn't known
/home/remi/dev/cpython_test/Modules/socketmodule.c:2935: warning: unused variable 'iov'
/home/remi/dev/cpython_test/Modules/socketmodule.c: In function 'sock_recvmsg_into':
/home/remi/dev/cpython_test/Modules/socketmodule.c:3023: error: invalid application of 'sizeof' to incomplete type 'struct iovec' 
/home/remi/dev/cpython_test/Modules/socketmodule.c:3023: warning: division by zero
/home/remi/dev/cpython_test/Modules/socketmodule.c:3023: error: invalid application of 'sizeof' to incomplete type 'struct iovec' 
/home/remi/dev/cpython_test/Modules/socketmodule.c:3034: error: invalid use of undefined type 'struct iovec'
/home/remi/dev/cpython_test/Modules/socketmodule.c:3034: error: dereferencing pointer to incomplete type
/home/remi/dev/cpython_test/Modules/socketmodule.c:3035: error: invalid use of undefined type 'struct iovec'
/home/remi/dev/cpython_test/Modules/socketmodule.c:3035: error: dereferencing pointer to incomplete type
/home/remi/dev/cpython_test/Modules/socketmodule.c: In function 'sock_sendmsg':
/home/remi/dev/cpython_test/Modules/socketmodule.c:3332: error: invalid application of 'sizeof' to incomplete type 'struct iovec' 
/home/remi/dev/cpython_test/Modules/socketmodule.c:3332: warning: division by zero
/home/remi/dev/cpython_test/Modules/socketmodule.c:3332: error: invalid application of 'sizeof' to incomplete type 'struct iovec' 
/home/remi/dev/cpython_test/Modules/socketmodule.c:3343: error: invalid use of undefined type 'struct iovec'
/home/remi/dev/cpython_test/Modules/socketmodule.c:3343: error: dereferencing pointer to incomplete type
/home/remi/dev/cpython_test/Modules/socketmodule.c:3344: error: invalid use of undefined type 'struct iovec'
/home/remi/dev/cpython_test/Modules/socketmodule.c:3344: error: dereferencing pointer to incomplete type
*** WARNING: renaming "_ssl" since importing it failed: No module named '_socket'

If I add a #include <sys/uio.h>, these 2 modules correcly build.

Attached file are:
-the diff
-the details of errors.

Thanks,
Remi.